Liquid crystal display (LCD) panels, particularly color LCD panels, are used for flat screen televisions, projection television systems and camcorder view finders, with many more applications anticipated in the future.
The fabrication of an active matrix liquid crystal display involves several steps. In one step, the front glass panel is prepared. This involves deposition of a color filter element onto a suitable substrate, such as glass. Color filter formation typically involves depositing a black matrix pattern and three primary (typically either red, green and blue or yellow, magenta and cyan) color dot or color cell patterns within the spaces outlined by the black matrix. The printed lines which form the black matrix typically are about 15-25 microns wide and about 0.5 to 2 microns thick. The red, green, and blue color cells are typically on the order of about 70-100 microns in width by 200 to 300 microns in length. The color cells are typically printed in films less than about 10 microns thick, and preferably less than 5 microns thick, and must be evenly applied and accurately registered within the pattern formed by the black matrix. The front glass substrate is typically completed by depositing a planarizing layer, a transparent conducting layer, and a polyimide alignment layer over the color filter element. The transparent conducting layer is typically indium tin oxide (ITO), although other materials can also be utilized.
In a second step, a separate (rear) glass panel is used for the formation of thin film transistors (TFT's) or diodes, as well as metal interconnect lines. Each transistor acts as an on-off switch for an individual color pixel in the display panel. The third and final step is the assembly of the two panels, including injection of a liquid crystal material between the two panels to form the liquid crystal panel.
One challenge to making the red, green and blue color pixel dots (also referred to as color cells) of the color filter is preventing the different colored inks from mixing with one another. In the past, this problem has been solved by first forming the black matrix pattern on a glass substrate (such as by photolithography) and then depositing the colors within the black matrix pattern.
It would be desirable to provide alternative methods for making color filters which have good resolution and registration, and which can be obtained easily and at a lower cost than prior art color filter arrays. It would also be desirable to achieve these qualities using a process which takes less steps than current processes.